1. ¹Department of Microbiology, Immunology and Pathology, Colorado State University, Fort, Collins, Colorado, USA
2. ²Division of Molecular Biology, Beckman Research Institute of the City of Hope, Duarte, California, USA

Correspondence: Ramesh Akkina, Department of Microbiology, Immunology and Pathology, Colorado State University, 1619 Campus Delivery, Fort Collins, Colorado 80523, USA. E-mail: akkina@colostate.edu

Received 1 November 2006; Accepted 27 December 2007; Published online 3 April 2007.

Abstract

Gene therapeutic strategies show promise in controlling human immunodeficiency virus (HIV) infection and in restoring immunological function. A number of efficacious anti-HIV gene constructs have been described so far, including small interfering RNAs (siRNAs), RNA decoys, transdominant proteins, and ribozymes, each with a different mode of action. However, as HIV is prone to generating escape mutants, the use of a single anti-HIV construct would not be adequate to afford long range-viral protection. On this basis, a combination of highly potent anti-HIV genes—namely, a short hairpin siRNA (shRNA) targeting rev and tat, a transactivation response (TAR) decoy, and a CCR5 ribozyme—have been inserted into a third-generation lentiviral vector. Our recent in vitro studies with this construct, Triple-R, established its efficacy in both T-cell lines and CD34 cell–derived macrophages. In this study, we have evaluated this combinatorial vector in vivo. Vector-transduced CD34 cells were injected into severe combined immunodeficiency (SCID)-hu mouse thy/liv grafts to determine their capacity to give rise to T cells. Our results show that phenotypically normal transgenic T cells are generated that are able to resist HIV-1 infection when challenged in vitro. These important attributes of this combinatorial vector show its promise as an excellent candidate for use in human clinical trials.